Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $60.79   12.111%   $68.1523   $68.15   $68.15   $68.20  
  Purchase #2 $103.87   5.802%   $109.8965   $109.90   $109.90   $109.90  
  Purchase #3 $170.49   9.800%   $187.198   $187.20   $187.20   $187.20  
  Purchase #4 $186.33   4.868%   $195.4005   $195.40   $195.40   $195.40  
  Purchase #5 $164.41   8.417%   $178.2484   $178.25   $178.25   $178.20  
  Purchase #6 $70.64   13.498%   $80.175   $80.18   $80.20   $80.20  
  Purchase #7 $219.72   6.361%   $233.6964   $233.70   $233.70   $233.70  
  7 purchase totals = $976.25       $1,052.7671   $1,052.78   $1,052.80   $1,052.80